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The Research Of The Sensitivity Enhancement Of Micro-structured Fiber Bragg Grating Based On Femtosecond Laser Processing

Posted on:2017-04-07Degree:MasterType:Thesis
Country:ChinaCandidate:B LiuFull Text:PDF
GTID:2428330566452665Subject:Mechanical engineering
Abstract/Summary:PDF Full Text Request
Compared with conventional electric sensors,fiber Bragg grating(FBG)sensor has the advantages of compact structure,high sensitivity,strong anti-interference ability,good repeatability,low energy and stability requirements of the light source,and so on.Application of sensitive coating on the surface of the fiber grating cladding has become a new trend towards enhancing FBG sensor performance.However,the existing coating on the surface of standard FBG has low sensitivity and the film is adhesiveness to the fiber suffer embrittlement,thus,high precision measurement is not achieved.This paper presents a new method of using femtosecond laser to process micro structure on the surface of FBG cladding to develop a novel micro-structured FBG sensor,the sensor has the advantages of high sensitivity and the thin film is not easy to fall off.The characteristics of micro structure FBG sensor are analyzed from two aspects of temperature and strain.The temperature aspect is achieved the development of FBG temperature sensor which is prepared by the magnetron sputtering method.The strain aspect is verified by the FBG magnetic field sensor,which uses TbDyFe magnetostrictive effect.In this paper,the principle of FBG sensor is described,the laser ablation technique introduced,the sensitivity enhancement of micro structure FBG is analyzed by methods of simulation and theoretical analysis.The optimization of femtosecond laser processing parameters and HF acid corrosion on different fiber cladding micro structure shapes is analyzed,the sputtering process and material deposition is described.Finally,the performance of the sensor probes is tested,the advantages and disadvantages of various micro structure probes are analyzed,and the overall optimization and improvement methods are put forward.The main research contents and results are as follows:(1)Firstly,the principle of temperature and strain sensitivity enhancement of micro structure FBG was analyzed,its feasibility is proved.Four kinds of micro structure models were designed.The micro structures development technique that combines optical fiber rotating fixture and the three-dimensional translation platform is introduced.The feasibility of these structures is analyzed by comparing the cross section area of the micro structure fiber and coating film,and the main structural parameters are confirmed using ANSYS.Then the finite element analysis method was used to verify the sensitivity enhancement and increase the range of the structure.The results show that these micro structures can effectively improve the sensitivity of the sensor.(2)The effect of laser processing parameters(aperture size,laser power,and scanning speed)on micro structure machining are explored in detail through experimental study and the suitable range of machining parameters are confirmed.The effects of HF acid concentration and etching time on the shape and surface quality of the micro structure are investigated,and the appropriate HF acid corrosion parameters are determined.In the end,the copper film or magnetostrictive film was deposited on the microstructure FBG by the magnetron sputtering method,and the sensor probes are fabricated.(3)The temperature and magnetic field sensors' probe performance test kit platform is established.The experimental results show that the amplitude of sensitivity of the probes with different microstructures or different processing parameters are different,in which the sensitivity of the temperature increased by 1.5~3 times and the magnetic field increased by 2~4 times,it means that processing the micro structures on the surface of FBG cladding can effectively improve the temperature and strain sensing properties of the sensor.
Keywords/Search Tags:fiber Bragg grating, sensitivity enhancement, micro-structure, femtosecond laser, HF acid corrosion
PDF Full Text Request
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